Palladium (II) - Catalyzed C3-Selective Friedel-Crafts Reaction of Indoles with Aziridines

The [PdCl2(MeCN)2]-catalyzed C3-selective Friedel-Crafts reaction of 2,2-disubstituted and 2-aryl-N-tosylaziridines with indoles is reported. For the 2,2-disubstituted substrates, [PdCl2(MeCN)2] alone, without any ancillary ligands, is an efficient catalyst for the ring-opening reaction. The presence of 1,4-benzoquinone as an additive was found to enhance the ring-opening reaction of the less-reactive 2-arylaziridines. This reaction displayed a broad substrate scope with respect to the indole substrate and is operationally simple. Finally, when 1,3-dimethylindole was employed as a substrate, the de-aromatized pyrroloindoline product was obtained in high yield and good diastereoselectivity

A mechanochemical zinc-mediated barbier-type allylation reaction under ball-milling conditions

A ball-milling-enabled zinc-mediated Barbier-type allylation reaction is reported. Notably, running the reaction in this manner renders it effective irrespective of the initial morphology of the zinc metal. The process is operationally simple, does not require inert atmospheres or dry solvents, and is reported over a range of aldehyde and ketone substrates; a gram-scale process is demonstrated

Palladium-catalysed reactions of aziridines and cyclopropanes

Strained-ring systems including vinylcyclopropanes, phenyl- and vinylaziridines were utilised to undergo ring-opening reactions under the catalysis of organotransition-metals in this research. Firstly, PdCl2(MeCN)2 catalysed the formal [3+2] annulations of N-activated aziridines to construct a number of potentially bioactive pyrroloindolines in one-pot with C3-substituted indoles. Furthermore, C3-unsubstituted indoles were treated with N-tosyl arylaziridines in the presence of PdCl2(MeCN)2 via a Friedel–Crafts pathway. The resulting β-substituted tryptamines then undergo the ring-closure with N-fluorobenzenesulfonimide to produce C3-fluorinated pyrroloindolines in moderate yields and selectivities. In chapter 2, the palladium(II)-catalysed addition of arylboronic acids to N-activated vinylaziridines has been developed. This reaction proceeds via a redox-neutral insertion/ring-opening process to provide unusual (Z)-allylsulfonamides preferentially. Finally, a highly efficient ring-opening reaction of vinylcyclopropanes by boronic acids was reported in the chapter 3, using palladium nanoparticles formed from Pd(OAc)2 and boronic acids in neat water. Linear and branched regioselectivities were obtained using vinylcyclopropanes and aryl-substituted vinylcyclopropanes respectively under these ligandless conditions

Unusual (Z)-selective palladium(II)-catalysed addition of aryl boronic acids to vinylaziridines

The palladium(II)-catalysed addition of arylboronic acids to vinylaziridines has been developed. This reaction proceeds via an insertion/ring-opening process to provide (Z)-allylsulfonamides preferentially. This stereoselectivity is complimentary to existing methods that typically proceed via a SN2′ mechanism to yield (E)-allylsulfonamides. Electron-deficient arylboronic acids were the optimum substrates for this reaction, while electron-donating groups on the aromatic ring of the boronic acids resulted in moderate yields

Ring-opening of vinylcyclopropane-1,1-dicarboxylates by boronic acids under ligandless palladium catalysis in neat water

We report a highly efficient ring-opening reaction of vinylcydopropanes by boronic acids in water, using palladium nanoparticles formed from Pd(OAc)(2) under ligandless conditions. Unsubstituted vinylcydopropanes provide linear addition products with high selectivity, while a switch in regioselectivity to branched products is observed for aryl-substituted vinylcydopropanes

Ring-Opening of Vinylcyclopropane-1,1-dicarboxylates by Boronic Acids under Ligandless Palladium Catalysis in Neat Water

We report a highly efficient ring-opening reaction of vinylcyclopropanes by boronic acids in water, using palladium nanoparticles formed from Pd­(OAc)₂ under ligandless conditions. Unsubstituted vinylcyclopropanes provide linear addition products with high selectivity, while a switch in regioselectivity to branched products is observed for aryl-substituted vinylcyclopropanes

A Load-Shedding Model Based on Sensitivity Analysis in on-Line Power System Operation Risk Assessment

The traditional load-shedding models usually use global optimization to get the load-shedding region, which will cause multiple variables, huge computing scale and other problems. This makes it hard to meet the requirements of timeliness in on-line power system operation risk assessment. In order to solve the problems of the present load-shedding models, a load-shedding model based on sensitivity analysis is proposed in this manuscript. By calculating the sensitivity of each branch on each bus, the collection of buses which have remarkable influence on reducing the power flow on over-load branches is obtained. In this way, global optimization is turned to local optimization, which can narrow the solution range. By comprehensively considering the importance of load bus and adjacency principle regarding the electrical coupling relationship, a load-shedding model is established to get the minimum value of the load reduction from different kinds of load buses, which is solved by the primal dual interior point algorithm. In the end, different cases on the IEEE 24-bus, IEEE 300-bus and other multi-node systems are simulated. The correctness and effectiveness of the proposed load-shedding model are demonstrated by the simulation results

A Novel Short-Term Maintenance Strategy for Power Transmission and Transformation Equipment Based on Risk-Cost-Analysis

Current studies on preventive condition-based maintenance of power transmission and transformation equipment mainly focus on mid-term or long-term maintenance, and cannot meet the requirements of short-term especially temporary maintenance. In order to solve the defects of the present preventive maintenance strategies, according to the engineering application and based on risk-cost analysis, a short-term maintenance strategy is proposed in this manuscript. For the equipment working in bad health condition, its active maintenance costs and operation risk costs are evaluated, respectively. Then the latest maintenance time is calculated in accordance with the principle that its operation risk costs are no higher than active maintenance costs. Utilizing the latest maintenance time, the best maintenance time is calculated by setting the maximum relative earnings of postponing maintenance as the target, which provides the operation staffs with comprehensive maintenance-decision support. In the end, different cases on the IEEE 24-bus system are simulated. The effectiveness and advantages of the proposed strategy are demonstrated by the simulation results

Partially etched Bi2O2CO3 by metal chloride for enhanced reactive oxygen species generation : a tale of two strategies

Light-mediated reactive oxygen species generation with water and oxygen is generally regarded as a mild and efficient way for organic pollutants removal. However, it is highly difficult but desirable to construct a photochemical system with increased reactive oxygen species production. Herein, by using Bi2O2CO3 as a prototype, we devise a simple metal chloride-involved etching method to achieve better light absorption and charge carriers separation in a wide-band-gap semiconductor, thus giving rise to improved molecular oxygen activation. The improved photoinduced reactive oxygen species production is further verified by excellent photocatalytic degradation ability of RhB, TC and BPA under visible and ultraviolet light illumination. In addition, the metal chloride-induced strategies—heterojunction formation and cation doping—significantly affect the dynamics and transfer of carriers, which are advantageous to manipulate one-/two-electron pathway for producing reactive oxygen species.This work was financially supported by the National Natural Science Foundation of China (Nos. 21476098, 21471069, 21576123, and 21676128)

Isolation and Characterization of 1 β-Acetoxypolygodial from Tasmannia lanceolata

A metabolite identified as 1β-acetoxypolygodial was isolated from the leaves and stems of a single specimen of Tasmannia lanceolata along with the previously reported 1β-acetoxyisodrimeninol. The structure of 1β-acetoxypolygodial was assigned by NMR spectroscopy and supported by X-ray crystallography